Jin Z, Zhuo H B, Nakazawa T, Shin J H, Wakamatsu S, Yugami N, Hosokai T, Zou D B, Yu M Y, Sheng Z M, Kodama R
Photon Pioneers Center, Osaka University, 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan.
College of Science, National University of Defense Technology, Changsha 410073, People's Republic of China.
Phys Rev E. 2016 Sep;94(3-1):033206. doi: 10.1103/PhysRevE.94.033206. Epub 2016 Sep 21.
Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ∼10.5mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7%. The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.
利用单脉冲太赫兹时域光谱系统记录了由超高对比度超短相对论激光脉冲辐照的薄箔片后产生的径向极化强太赫兹（THz）辐射。随着靶厚度从30μm减小到2μm，太赫兹辐射的持续时间从5ps增加到超过20ps，并且辐射能量急剧增加，达到每脉冲约10.5mJ，对应激光到太赫兹辐射的能量转换效率为1.7%。高效的太赫兹辐射可归因于靶后鞘层电场对激光驱动热电子的反射（减速和加速）。实验结果与一个简单模型以及粒子模拟的结果一致。
